The present invention relates to a cylinder liner support arrangement in an internal combustion engine, and particularly an internal combustion engine having at least two in-line combustion chambers.
The cylinder liner support of the invention is particularly intended for use in internal combustion engines in which the cylinder block (engine block) and associated cylinder head are made in a single continuous piece, commonly called a monobloc element or simply a monobloc. In such an engine, the cylinder liners (which form cylinder barrels for the pistons) have their upper portions inserted in cavities (cylinder bores) in the cylinder block.
The cylinder liner support of the invention may nevertheless also be used in internal combustion engines in which the cylinder block is separate from the cylinder head, in which case the cylinder liner support is separate from the crankshaft retaining portion (crankcase) of the engine.
In a conventional internal combustion engine in which the cylinder block (engine block) and cylinder head (top cap) are separate elements, the cylinder head is fastened on top of the cylinder block by means of studbolts or other types of fastening screws. The valve seat machining required for such a conventional engine involves no great difficulties, since in this case the valve seats are situated in the "roof" of the combustion chamber, i.e., on the underside of the cylinder head. This makes the valve seats readily accessible for machining from the underside of the cylinder head.
In the contrasting case of internal combustion engines of the kind indicated in the introduction, i.e., monobloc engines in which the cylinder head and cylinder block consist of a single undivided constructional element, valve seat machining involves great difficulties. This is because, in this case, the valve seats are situated deep inside the monobloc, more precisely in the roof of the combustion chamber, i.e., at the top of the respective cylinders. The valve seats are thus situated just above the extreme top ends of the cylinders, i.e., just above the extreme top ends of the cylinder bores which are incorporated in the monobloc and in which the cylinder liners have to be fastened.
Machining the valve seats in this case has to be done by means of tools introduced into the monobloc from below, more precisely, up through the cylinders/cylinder bores in the monobloc. As machining the valve seats in such an engine does, of course, take place before the cylinder liners have been fitted in the cylinder bores, the "working distance" through a cylinder bore is not as great as the axial length of the cylinder liner, which is longer, and is determined instead by the total axial length of the actual cylinder bore or the portions of the monobloc which form the receiving cavity and support for the cylinder liner. The axial working distance available for valve seat machining, calculated upwards from the underside of the lowest portions of the monobloc in the region of the cylinders, will certainly be smaller if only a shorter upper portion of the cylinder liner has to be fastened in and provided with support, but at least the upper half of the cylinder liner has, for thermal and strength reasons, to be liquid-cooled (water-cooled), i.e., fixed in a cavity which is surrounded by cooling liquid ducts in the region of the monobloc which forms the cylinder block portion.
Previously known from U.S. Pat. No. 4,294,203 is an internal combustion engine of monobloc type in which the cylinder head and cylinder block consist of one integrated element and the cavity in the engine which accommodates each cylinder liner is divided into an upper portion situated in the monobloc and a lower portion situated in an upwardly extended reinforced upper portion of the engine crankcase. However, an obvious disadvantage of such a design solution is that it requires a heavier crankcase portion which will also be of more complicated design and therefore more expensive to produce.